The present invention relates to a data recording/reproducing apparatus for recording and reproducing high density data, and more particularly, to a helical scan type VTR for recording image data at a high resolution in a parallel fashion and reproducing the same in a serial fashion.
In the field of picture information processing, there has been a demand for recording/reproducing a picture at a high resolution, for example, with the number of scanning lines at 1,000 or more. Let us consider a case in which a high resolution in which the number of picture elements is 1,000.times.1,000, for example, is obtained by using a solid-state image pickup device such as a two dimensional MOS image sensor. In this case, it is assumed that 1 .mu.s is taken for reading out data per photoelectric cell forming a picture element in an image sensor. For reading out all data in the 1,000.times.1,000 cells, 10.sup.6 .mu.s, or 1 sec, is taken. Thus, there is a time lag of one second from the instant that the first cell data is read out until the 10.sup.6 -th cell data is read out. The cell data correspond to an amount of charge and the charge amount is substantially proportional to an amount of radiated light, or an exposure time. For this reason, there is a large sensitivity difference between the photoelectric transfer sensitivity (stored charge amount) of the first cell and that of the 10.sup.6 -th cell, resulting in a great deterioration of the picture quality. In an extreme case, the saturation of the cell takes place during the reading of the picture data, failing to have a proper picture data.
The problem can be solved in the following way. As shown in FIG. 1, an image sensor 10 or 1,000.times.1,000 cells is divided into four imaging blocks 10.sub.1 to 10.sub.4, each block having 1,000 cells.times.250 cells, for example. One imaging block can be considered to have 250 lines each containing 1,000 picture elements. 1,000 cells on each horizontal scanning line are equidistantly arranged thereby to obtain 1,000 vertical scanning lines. Four output signals VA1 to VA4 from a vertical address shift register 12 are applied to each of the blocks 10.sub.1 to 10.sub.4. Horizontal addresses of the blocks 10.sub.1 to 10.sub.4 are specified by an output signal HA from a horizontal address shift register 14. The vertical scannings of the blocks 10.sub.1 to 10.sub.4 are performed in a parallel fashion by the four output signals VA1 to VA4. All the horizontal scannings of the blocks 10.sub.1 to 10.sub.4 are simultaneously performed by the signal HA. In this way, the picture data of the four blocks can be obtained parallel or time-divisionally.
As described above, when one picture screen is divided into four parallel picture data, the scanning time of one picture can be reduced to 1/4 second. Further, if the number of the divided picture data is 16, the picture data of one picture screen can be taken out for 1/16 second. In this way, the deterioration of the picture quality due to a variation of the cell sensitivity can be limited to a low degree. For recording the parallel divided picture data into an ordinary helical scan type VTR, the data must be subjected to the parallel to serial data conversion. More particularly, the four parallel data are temporarily stored into memories of four blocks, and then these data are sequentially read out to provide serial picture data. Such memory requires a large capacity and a relatively high speed operation, and therefore is expensive.